Alloy



Oct. 16, 1928.

J. A. GANN ALLOY Filed octjzv'. 1921 INVENTOR.

BY e9?, q @f ATToRNEYd vPatented Oct. 16, 1928".

UNITED STATE-s PATENT OFFICE.

JOHN A. GAN N, F MIDLAND, MICHIGAN, ASSIGNOR T0 THE DOW CHEMICAL COMPANY, `01E MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN.

ALLOY.

i Application led October 2 7, 1921. Serial No. 510,797.

The present improved alloy is one in which magnesium is the predominant element, the object being to develop an alloy that will possess the characteristic lightness which isobtained by the use of magnesium in excess o'80 per cent, while such alloy will be character'- ized by high strength and high toughness and hardness sufficient for satisfactory use in the pistons of internal combustion vengines for example. It is not intended, however, to limit the field of use in the mechanical arts to which an alloy possessing the lightness and physical characteristics of the one in hand may be applied. Primarily, the present improved alloy contains, in addition to magnesium in the predominant proportion indicated, aluminum and copper, thus constituting a ternary alloy. However, the characteristics ofthe alloy may be modified by the addition of further metals, specifically one or more of thc following, viz, cadmium, tin and zinc, in relatively small amounts.

I he present invention accordingly consists of such ternary alloy with or without the addition of such further metals, together with the steps involved inthe making of such alloy hereinafter fully described and particu-l larly pointed out in the claims. The annexed drawing and following description it will be understood set forth but oney of several ways in which the invention may be carried out.

In said annexed drawing rI`he single ligure. there appearing is a diagrammatic representation of certain physical properties discovered-in a typicalternary magnesium-aluminum-copper alloy of the class in hand, wherein the copper content remains constant while the aluminum content varies.

In such diagrammatic figure the physical properties represented, it will be noted, are the impact-toughness, hardness and tensilestrength, such impact-toughness being determined by the single-blow method and the hardness by the Brinell method and scaled to correspond with such impact-roughness. The curves in the diagram are not necessarily accurate representations throughout of the exact response of such alloy to tests of the character described, but do represent the manner in which the characteristic properties in question vary throughout the range under consideration which, as already indicated, in-

cludes not less than 80 per cent of magnesium, the balance being made up of aluminum and copper with or without the addition in smaller amount of one or more of the :t'ollowing, viz,"cadmium, tin and zinc.

For a ternary alloy that will be properly balanced with respect to the characteristics 1n question and at the same time have a suiciently high thermal conductivity to adapt same for use in pistons in internal combustion motors, I prefer to use magnesium 90 per cent; aluminum 9 per cent and copper 1 per cent. Castings made from such alloy-Will have a specific gravity of approximately 1.80; tensile strength of approximately 17000 pounds per square inch; Brinell hardness of 52; and single-blow impact-'toughness of 30.

Ilor certain conditions of use, I find that the amount of the aluminum may be slightly reduced and cadmium, tin or Zinc added, thus making a quarternary alloy. A satisfactory formula for this type will consist of magnesium 90 per cent; aluminum 8 per cent; copper 1 per cent and cadmium (or tin or zinc, as the case may be) 1 per cent.

p As an alternative to reducing the relative proportion or aluminum, the amount of magnesium may be reduced and instead of adding but one additional ingredient, two metals, for example, cadmium and zinc, may be added with excellent results. The following is ai formula for such a quinary alloy, viz, magnesium 87.85 per cent; aluminum 8.50 per cent; copper 2 per cent; cadmium 1 per cent 4and zinc 0.65 per cent.

To make my improved alloy, a measured quantity of pure magnesium metal is lirst melted in a suitable pot along with a proper amount of a iiux that, while heavier than such metal, will have proper surface tension to promptly and effectively coat the metal. As an example of such a linx, approximately equal part-s `of anhydrous magnesium chloride and sodium chloride may be employed, and if the specific gravity of such flux proves inadequate to ioat the metal after it has been alloyed, a small amount of barium chloride may be added. .A small amount of the molten magnesium metal is then taken up in a ladle and the Iwhole or part of the alumi- -num and copper, depending upon the total percentage thereof to be added to the batch, is placed in such ladle and melted with the magnesium therein, thereby producing an alloy relatively high in the alloying ingredients. The contents ci the ladle are then gradually added to the main body of molten magnesium, (the operation being repeated until all of the alloying ingredients are added), with' the result that the aluminum and copper forming such ingredients will diffuse throughout the mass and not drop through into the body of flux in which the latter floats and so be lost. As soon as the introduction of such alloying ingredients has been thus effected, the whole mass is well puddled and the operation may then be rep garded as complete and the molten alloy cast along withsuch two in forming the preliminary alloy which is subsequently added to the main body of the molten magnesium metal,

resulting in the production of an alloy 1n which such magnesium is the predominant ingredient. On the other hand, in some cases such additional ingredients may be conven iently combined with each other before being thus alloyed with magnesium, the final result of course being the same.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the steps herein disclosed or the ingredients employed in carrying out such steps, provided the steps or ingredients set forth in the following claims or the equivalent of such steps or ingredients be employed.

I therefore particularly point out and distinctly claim as my invention l. As a new product, an alloy containing approximately ninety per cent of magnesium, nine per cent of aluminum, and less than one and one-half per cent of copper.

2. As a new product, an alloy containing approximately ninety per cent of magnesium, nine per cent of aluminum, and copper, cadmium and zinc eac-h in small but consequential percentages.

3. The method of making a magnesiumaluminum-copper alloy, wherein the magnesium largely predominates, which consists in first interfusing the desired amount of aluminum and the desired amount of copper with a relatively small quantity of the total magnesium in such alloy, and then adding the resulting alloy to the remaining quantity of magnesium in molten state.

4. The method of making a magnesiumaluminum-copper alloy, wherein the magnesiumlargely predominates, which consists in first interfusing the desired amount of aluminum and the desired amount of copper withva relatively small quantity of the total magnesium in such alloy, whereby an alloy relatively high in aluminum and copper is produced, and then adding such resulting alloy to the remaining quantity of magnesium. f 

